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GKN Driveline

Two-speed gearbox for electric vehicle applications

GKN has successfully developed the world’s first two speed eAxle. In just 24 months the innovation for electric vehicles was taken from conception to vehicle integration in a truly class redefining hybrid sports car – the BMW i8. Potential follow on applications of this innovation include enabling a more holistic approach to optimizing all-electric powertrains to delivering hybrid and AWD capabilities in developed platforms without major structural changes. Weight, refinement and efficiency were core to the development of the clutchless 2-speed eAxle. By giving electric motors additional gear ratios, not only can higher running speeds be attained, balanced with exciting acceleration and improved range, but associated systems such as the motor and power electronics can be downsized. The compact electromechanically actuated eAxle is weight optimized to only 27kg, yet is robust enough to transmit over 2800Nm of torque from launch. As vehicle manufacturers explore opportunities to lower vehicle weight with new materials, the NVH sensitivity of vehicles is increased. The synchronized eAxle balances high gear shift comfort with low gear whine noise, and the package is over 97% efficient. Its unique layout ensures the highest torque density.

Integrated initially into the BMW i8, the software controlling the eAxle, developed wholly in house, is so deeply embedded that the vehicle actually hands over complete control of the front axle to the GKN system when a gear shift is required. Once the gear change has been effected the system hands control back over to the BMW system.